Documentation/usb/gadget-testing.rst

   1 ==============
   2 Gadget Testing
   3 ==============
   4
   5 This file summarizes information on basic testing of USB functions
   6 provided by gadgets.
   7
   8 .. contents
   9
  10    1. ACM function
  11    2. ECM function
  12    3. ECM subset function
  13    4. EEM function
  14    5. FFS function
  15    6. HID function
  16    7. LOOPBACK function
  17    8. MASS STORAGE function
  18    9. MIDI function
  19    10. NCM function
  20    11. OBEX function
  21    12. PHONET function
  22    13. RNDIS function
  23    14. SERIAL function
  24    15. SOURCESINK function
  25    16. UAC1 function (legacy implementation)
  26    17. UAC2 function
  27    18. UVC function
  28    19. PRINTER function
  29    20. UAC1 function (new API)
  30
  31
  32 1. ACM function
  33 ===============
  34
  35 The function is provided by usb_f_acm.ko module.
  36
  37 Function-specific configfs interface
  38 ------------------------------------
  39
  40 The function name to use when creating the function directory is "acm".
  41 The ACM function provides just one attribute in its function directory:
  42
  43         port_num
  44
  45 The attribute is read-only.
  46
  47 There can be at most 4 ACM/generic serial/OBEX ports in the system.
  48
  49
  50 Testing the ACM function
  51 ------------------------
  52
  53 On the host::
  54
  55         cat > /dev/ttyACM<X>
  56
  57 On the device::
  58
  59         cat /dev/ttyGS<Y>
  60
  61 then the other way round
  62
  63 On the device::
  64
  65         cat > /dev/ttyGS<Y>
  66
  67 On the host::
  68
  69         cat /dev/ttyACM<X>
  70
  71 2. ECM function
  72 ===============
  73
  74 The function is provided by usb_f_ecm.ko module.
  75
  76 Function-specific configfs interface
  77 ------------------------------------
  78
  79 The function name to use when creating the function directory is "ecm".
  80 The ECM function provides these attributes in its function directory:
  81
  82         =============== ==================================================
  83         ifname          network device interface name associated with this
  84                         function instance
  85         qmult           queue length multiplier for high and super speed
  86         host_addr       MAC address of host's end of this
  87                         Ethernet over USB link
  88         dev_addr        MAC address of device's end of this
  89                         Ethernet over USB link
  90         =============== ==================================================
  91
  92 and after creating the functions/ecm.<instance name> they contain default
  93 values: qmult is 5, dev_addr and host_addr are randomly selected.
  94 Except for ifname they can be written to until the function is linked to a
  95 configuration. The ifname is read-only and contains the name of the interface
  96 which was assigned by the net core, e. g. usb0.
  97
  98 Testing the ECM function
  99 ------------------------
 100
 101 Configure IP addresses of the device and the host. Then:
 102
 103 On the device::
 104
 105         ping <host's IP>
 106
 107 On the host::
 108
 109         ping <device's IP>
 110
 111 3. ECM subset function
 112 ======================
 113
 114 The function is provided by usb_f_ecm_subset.ko module.
 115
 116 Function-specific configfs interface
 117 ------------------------------------
 118
 119 The function name to use when creating the function directory is "geth".
 120 The ECM subset function provides these attributes in its function directory:
 121
 122         =============== ==================================================
 123         ifname          network device interface name associated with this
 124                         function instance
 125         qmult           queue length multiplier for high and super speed
 126         host_addr       MAC address of host's end of this
 127                         Ethernet over USB link
 128         dev_addr        MAC address of device's end of this
 129                         Ethernet over USB link
 130         =============== ==================================================
 131
 132 and after creating the functions/ecm.<instance name> they contain default
 133 values: qmult is 5, dev_addr and host_addr are randomly selected.
 134 Except for ifname they can be written to until the function is linked to a
 135 configuration. The ifname is read-only and contains the name of the interface
 136 which was assigned by the net core, e. g. usb0.
 137
 138 Testing the ECM subset function
 139 -------------------------------
 140
 141 Configure IP addresses of the device and the host. Then:
 142
 143 On the device::
 144
 145         ping <host's IP>
 146
 147 On the host::
 148
 149         ping <device's IP>
 150
 151 4. EEM function
 152 ===============
 153
 154 The function is provided by usb_f_eem.ko module.
 155
 156 Function-specific configfs interface
 157 ------------------------------------
 158
 159 The function name to use when creating the function directory is "eem".
 160 The EEM function provides these attributes in its function directory:
 161
 162         =============== ==================================================
 163         ifname          network device interface name associated with this
 164                         function instance
 165         qmult           queue length multiplier for high and super speed
 166         host_addr       MAC address of host's end of this
 167                         Ethernet over USB link
 168         dev_addr        MAC address of device's end of this
 169                         Ethernet over USB link
 170         =============== ==================================================
 171
 172 and after creating the functions/eem.<instance name> they contain default
 173 values: qmult is 5, dev_addr and host_addr are randomly selected.
 174 Except for ifname they can be written to until the function is linked to a
 175 configuration. The ifname is read-only and contains the name of the interface
 176 which was assigned by the net core, e. g. usb0.
 177
 178 Testing the EEM function
 179 ------------------------
 180
 181 Configure IP addresses of the device and the host. Then:
 182
 183 On the device::
 184
 185         ping <host's IP>
 186
 187 On the host::
 188
 189         ping <device's IP>
 190
 191 5. FFS function
 192 ===============
 193
 194 The function is provided by usb_f_fs.ko module.
 195
 196 Function-specific configfs interface
 197 ------------------------------------
 198
 199 The function name to use when creating the function directory is "ffs".
 200 The function directory is intentionally empty and not modifiable.
 201
 202 After creating the directory there is a new instance (a "device") of FunctionFS
 203 available in the system. Once a "device" is available, the user should follow
 204 the standard procedure for using FunctionFS (mount it, run the userspace
 205 process which implements the function proper). The gadget should be enabled
 206 by writing a suitable string to usb_gadget/<gadget>/UDC.
 207
 208 Testing the FFS function
 209 ------------------------
 210
 211 On the device: start the function's userspace daemon, enable the gadget
 212
 213 On the host: use the USB function provided by the device
 214
 215 6. HID function
 216 ===============
 217
 218 The function is provided by usb_f_hid.ko module.
 219
 220 Function-specific configfs interface
 221 ------------------------------------
 222
 223 The function name to use when creating the function directory is "hid".
 224 The HID function provides these attributes in its function directory:
 225
 226         =============== ===========================================
 227         protocol        HID protocol to use
 228         report_desc     data to be used in HID reports, except data
 229                         passed with /dev/hidg<X>
 230         report_length   HID report length
 231         subclass        HID subclass to use
 232         =============== ===========================================
 233
 234 For a keyboard the protocol and the subclass are 1, the report_length is 8,
 235 while the report_desc is::
 236
 237   $ hd my_report_desc
 238   00000000  05 01 09 06 a1 01 05 07  19 e0 29 e7 15 00 25 01  |..........)...%.|
 239   00000010  75 01 95 08 81 02 95 01  75 08 81 03 95 05 75 01  |u.......u.....u.|
 240   00000020  05 08 19 01 29 05 91 02  95 01 75 03 91 03 95 06  |....).....u.....|
 241   00000030  75 08 15 00 25 65 05 07  19 00 29 65 81 00 c0     |u...%e....)e...|
 242   0000003f
 243
 244 Such a sequence of bytes can be stored to the attribute with echo::
 245
 246   $ echo -ne \\x05\\x01\\x09\\x06\\xa1.....
 247
 248 Testing the HID function
 249 ------------------------
 250
 251 Device:
 252
 253 - create the gadget
 254 - connect the gadget to a host, preferably not the one used
 255   to control the gadget
 256 - run a program which writes to /dev/hidg<N>, e.g.
 257   a userspace program found in Documentation/usb/gadget_hid.rst::
 258
 259         $ ./hid_gadget_test /dev/hidg0 keyboard
 260
 261 Host:
 262
 263 - observe the keystrokes from the gadget
 264
 265 7. LOOPBACK function
 266 ====================
 267
 268 The function is provided by usb_f_ss_lb.ko module.
 269
 270 Function-specific configfs interface
 271 ------------------------------------
 272
 273 The function name to use when creating the function directory is "Loopback".
 274 The LOOPBACK function provides these attributes in its function directory:
 275
 276         =============== =======================
 277         qlen            depth of loopback queue
 278         bulk_buflen     buffer length
 279         =============== =======================
 280
 281 Testing the LOOPBACK function
 282 -----------------------------
 283
 284 device: run the gadget
 285
 286 host: test-usb (tools/usb/testusb.c)
 287
 288 8. MASS STORAGE function
 289 ========================
 290
 291 The function is provided by usb_f_mass_storage.ko module.
 292
 293 Function-specific configfs interface
 294 ------------------------------------
 295
 296 The function name to use when creating the function directory is "mass_storage".
 297 The MASS STORAGE function provides these attributes in its directory:
 298 files:
 299
 300         =============== ==============================================
 301         stall           Set to permit function to halt bulk endpoints.
 302                         Disabled on some USB devices known not to work
 303                         correctly. You should set it to true.
 304         num_buffers     Number of pipeline buffers. Valid numbers
 305                         are 2..4. Available only if
 306                         CONFIG_USB_GADGET_DEBUG_FILES is set.
 307         =============== ==============================================
 308
 309 and a default lun.0 directory corresponding to SCSI LUN #0.
 310
 311 A new lun can be added with mkdir::
 312
 313         $ mkdir functions/mass_storage.0/partition.5
 314
 315 Lun numbering does not have to be continuous, except for lun #0 which is
 316 created by default. A maximum of 8 luns can be specified and they all must be
 317 named following the <name>.<number> scheme. The numbers can be 0..8.
 318 Probably a good convention is to name the luns "lun.<number>",
 319 although it is not mandatory.
 320
 321 In each lun directory there are the following attribute files:
 322
 323         =============== ==============================================
 324         file            The path to the backing file for the LUN.
 325                         Required if LUN is not marked as removable.
 326         ro              Flag specifying access to the LUN shall be
 327                         read-only. This is implied if CD-ROM emulation
 328                         is enabled as well as when it was impossible
 329                         to open "filename" in R/W mode.
 330         removable       Flag specifying that LUN shall be indicated as
 331                         being removable.
 332         cdrom           Flag specifying that LUN shall be reported as
 333                         being a CD-ROM.
 334         nofua           Flag specifying that FUA flag
 335                         in SCSI WRITE(10,12)
 336         =============== ==============================================
 337
 338 Testing the MASS STORAGE function
 339 ---------------------------------
 340
 341 device: connect the gadget, enable it
 342 host: dmesg, see the USB drives appear (if system configured to automatically
 343 mount)
 344
 345 9. MIDI function
 346 ================
 347
 348 The function is provided by usb_f_midi.ko module.
 349
 350 Function-specific configfs interface
 351 ------------------------------------
 352
 353 The function name to use when creating the function directory is "midi".
 354 The MIDI function provides these attributes in its function directory:
 355
 356         =============== ====================================
 357         buflen          MIDI buffer length
 358         id              ID string for the USB MIDI adapter
 359         in_ports        number of MIDI input ports
 360         index           index value for the USB MIDI adapter
 361         out_ports       number of MIDI output ports
 362         qlen            USB read request queue length
 363         =============== ====================================
 364
 365 Testing the MIDI function
 366 -------------------------
 367
 368 There are two cases: playing a mid from the gadget to
 369 the host and playing a mid from the host to the gadget.
 370
 371 1) Playing a mid from the gadget to the host:
 372
 373 host::
 374
 375   $ arecordmidi -l
 376    Port    Client name                      Port name
 377    14:0    Midi Through                     Midi Through Port-0
 378    24:0    MIDI Gadget                      MIDI Gadget MIDI 1
 379   $ arecordmidi -p 24:0 from_gadget.mid
 380
 381 gadget::
 382
 383   $ aplaymidi -l
 384    Port    Client name                      Port name
 385    20:0    f_midi                           f_midi
 386
 387   $ aplaymidi -p 20:0 to_host.mid
 388
 389 2) Playing a mid from the host to the gadget
 390
 391 gadget::
 392
 393   $ arecordmidi -l
 394    Port    Client name                      Port name
 395    20:0    f_midi                           f_midi
 396
 397   $ arecordmidi -p 20:0 from_host.mid
 398
 399 host::
 400
 401   $ aplaymidi -l
 402    Port    Client name                      Port name
 403    14:0    Midi Through                     Midi Through Port-0
 404    24:0    MIDI Gadget                      MIDI Gadget MIDI 1
 405
 406   $ aplaymidi -p24:0 to_gadget.mid
 407
 408 The from_gadget.mid should sound identical to the to_host.mid.
 409
 410 The from_host.id should sound identical to the to_gadget.mid.
 411
 412 MIDI files can be played to speakers/headphones with e.g. timidity installed::
 413
 414   $ aplaymidi -l
 415    Port    Client name                      Port name
 416    14:0    Midi Through                     Midi Through Port-0
 417    24:0    MIDI Gadget                      MIDI Gadget MIDI 1
 418   128:0    TiMidity                         TiMidity port 0
 419   128:1    TiMidity                         TiMidity port 1
 420   128:2    TiMidity                         TiMidity port 2
 421   128:3    TiMidity                         TiMidity port 3
 422
 423   $ aplaymidi -p 128:0 file.mid
 424
 425 MIDI ports can be logically connected using the aconnect utility, e.g.::
 426
 427   $ aconnect 24:0 128:0 # try it on the host
 428
 429 After the gadget's MIDI port is connected to timidity's MIDI port,
 430 whatever is played at the gadget side with aplaymidi -l is audible
 431 in host's speakers/headphones.
 432
 433 10. NCM function
 434 ================
 435
 436 The function is provided by usb_f_ncm.ko module.
 437
 438 Function-specific configfs interface
 439 ------------------------------------
 440
 441 The function name to use when creating the function directory is "ncm".
 442 The NCM function provides these attributes in its function directory:
 443
 444         =============== ==================================================
 445         ifname          network device interface name associated with this
 446                         function instance
 447         qmult           queue length multiplier for high and super speed
 448         host_addr       MAC address of host's end of this
 449                         Ethernet over USB link
 450         dev_addr        MAC address of device's end of this
 451                         Ethernet over USB link
 452         =============== ==================================================
 453
 454 and after creating the functions/ncm.<instance name> they contain default
 455 values: qmult is 5, dev_addr and host_addr are randomly selected.
 456 Except for ifname they can be written to until the function is linked to a
 457 configuration. The ifname is read-only and contains the name of the interface
 458 which was assigned by the net core, e. g. usb0.
 459
 460 Testing the NCM function
 461 ------------------------
 462
 463 Configure IP addresses of the device and the host. Then:
 464
 465 On the device::
 466
 467         ping <host's IP>
 468
 469 On the host::
 470
 471         ping <device's IP>
 472
 473 11. OBEX function
 474 =================
 475
 476 The function is provided by usb_f_obex.ko module.
 477
 478 Function-specific configfs interface
 479 ------------------------------------
 480
 481 The function name to use when creating the function directory is "obex".
 482 The OBEX function provides just one attribute in its function directory:
 483
 484         port_num
 485
 486 The attribute is read-only.
 487
 488 There can be at most 4 ACM/generic serial/OBEX ports in the system.
 489
 490 Testing the OBEX function
 491 -------------------------
 492
 493 On device::
 494
 495         seriald -f /dev/ttyGS<Y> -s 1024
 496
 497 On host::
 498
 499         serialc -v <vendorID> -p <productID> -i<interface#> -a1 -s1024 \
 500                 -t<out endpoint addr> -r<in endpoint addr>
 501
 502 where seriald and serialc are Felipe's utilities found here:
 503
 504         https://github.com/felipebalbi/usb-tools.git master
 505
 506 12. PHONET function
 507 ===================
 508
 509 The function is provided by usb_f_phonet.ko module.
 510
 511 Function-specific configfs interface
 512 ------------------------------------
 513
 514 The function name to use when creating the function directory is "phonet".
 515 The PHONET function provides just one attribute in its function directory:
 516
 517         =============== ==================================================
 518         ifname          network device interface name associated with this
 519                         function instance
 520         =============== ==================================================
 521
 522 Testing the PHONET function
 523 ---------------------------
 524
 525 It is not possible to test the SOCK_STREAM protocol without a specific piece
 526 of hardware, so only SOCK_DGRAM has been tested. For the latter to work,
 527 in the past I had to apply the patch mentioned here:
 528
 529 http://www.spinics.net/lists/linux-usb/msg85689.html
 530
 531 These tools are required:
 532
 533 git://git.gitorious.org/meego-cellular/phonet-utils.git
 534
 535 On the host::
 536
 537         $ ./phonet -a 0x10 -i usbpn0
 538         $ ./pnroute add 0x6c usbpn0
 539         $./pnroute add 0x10 usbpn0
 540         $ ifconfig usbpn0 up
 541
 542 On the device::
 543
 544         $ ./phonet -a 0x6c -i upnlink0
 545         $ ./pnroute add 0x10 upnlink0
 546         $ ifconfig upnlink0 up
 547
 548 Then a test program can be used::
 549
 550         http://www.spinics.net/lists/linux-usb/msg85690.html
 551
 552 On the device::
 553
 554         $ ./pnxmit -a 0x6c -r
 555
 556 On the host::
 557
 558         $ ./pnxmit -a 0x10 -s 0x6c
 559
 560 As a result some data should be sent from host to device.
 561 Then the other way round:
 562
 563 On the host::
 564
 565         $ ./pnxmit -a 0x10 -r
 566
 567 On the device::
 568
 569         $ ./pnxmit -a 0x6c -s 0x10
 570
 571 13. RNDIS function
 572 ==================
 573
 574 The function is provided by usb_f_rndis.ko module.
 575
 576 Function-specific configfs interface
 577 ------------------------------------
 578
 579 The function name to use when creating the function directory is "rndis".
 580 The RNDIS function provides these attributes in its function directory:
 581
 582         =============== ==================================================
 583         ifname          network device interface name associated with this
 584                         function instance
 585         qmult           queue length multiplier for high and super speed
 586         host_addr       MAC address of host's end of this
 587                         Ethernet over USB link
 588         dev_addr        MAC address of device's end of this
 589                         Ethernet over USB link
 590         =============== ==================================================
 591
 592 and after creating the functions/rndis.<instance name> they contain default
 593 values: qmult is 5, dev_addr and host_addr are randomly selected.
 594 Except for ifname they can be written to until the function is linked to a
 595 configuration. The ifname is read-only and contains the name of the interface
 596 which was assigned by the net core, e. g. usb0.
 597
 598 Testing the RNDIS function
 599 --------------------------
 600
 601 Configure IP addresses of the device and the host. Then:
 602
 603 On the device::
 604
 605         ping <host's IP>
 606
 607 On the host::
 608
 609         ping <device's IP>
 610
 611 14. SERIAL function
 612 ===================
 613
 614 The function is provided by usb_f_gser.ko module.
 615
 616 Function-specific configfs interface
 617 ------------------------------------
 618
 619 The function name to use when creating the function directory is "gser".
 620 The SERIAL function provides just one attribute in its function directory:
 621
 622         port_num
 623
 624 The attribute is read-only.
 625
 626 There can be at most 4 ACM/generic serial/OBEX ports in the system.
 627
 628 Testing the SERIAL function
 629 ---------------------------
 630
 631 On host::
 632
 633         insmod usbserial
 634         echo VID PID >/sys/bus/usb-serial/drivers/generic/new_id
 635
 636 On host::
 637
 638         cat > /dev/ttyUSB<X>
 639
 640 On target::
 641
 642         cat /dev/ttyGS<Y>
 643
 644 then the other way round
 645
 646 On target::
 647
 648         cat > /dev/ttyGS<Y>
 649
 650 On host::
 651
 652         cat /dev/ttyUSB<X>
 653
 654 15. SOURCESINK function
 655 =======================
 656
 657 The function is provided by usb_f_ss_lb.ko module.
 658
 659 Function-specific configfs interface
 660 ------------------------------------
 661
 662 The function name to use when creating the function directory is "SourceSink".
 663 The SOURCESINK function provides these attributes in its function directory:
 664
 665         =============== ==================================
 666         pattern         0 (all zeros), 1 (mod63), 2 (none)
 667         isoc_interval   1..16
 668         isoc_maxpacket  0 - 1023 (fs), 0 - 1024 (hs/ss)
 669         isoc_mult       0..2 (hs/ss only)
 670         isoc_maxburst   0..15 (ss only)
 671         bulk_buflen     buffer length
 672         bulk_qlen       depth of queue for bulk
 673         iso_qlen        depth of queue for iso
 674         =============== ==================================
 675
 676 Testing the SOURCESINK function
 677 -------------------------------
 678
 679 device: run the gadget
 680
 681 host: test-usb (tools/usb/testusb.c)
 682
 683
 684 16. UAC1 function (legacy implementation)
 685 =========================================
 686
 687 The function is provided by usb_f_uac1_legacy.ko module.
 688
 689 Function-specific configfs interface
 690 ------------------------------------
 691
 692 The function name to use when creating the function directory
 693 is "uac1_legacy".
 694 The uac1 function provides these attributes in its function directory:
 695
 696         =============== ====================================
 697         audio_buf_size  audio buffer size
 698         fn_cap          capture pcm device file name
 699         fn_cntl         control device file name
 700         fn_play         playback pcm device file name
 701         req_buf_size    ISO OUT endpoint request buffer size
 702         req_count       ISO OUT endpoint request count
 703         =============== ====================================
 704
 705 The attributes have sane default values.
 706
 707 Testing the UAC1 function
 708 -------------------------
 709
 710 device: run the gadget
 711
 712 host::
 713
 714         aplay -l # should list our USB Audio Gadget
 715
 716 17. UAC2 function
 717 =================
 718
 719 The function is provided by usb_f_uac2.ko module.
 720
 721 Function-specific configfs interface
 722 ------------------------------------
 723
 724 The function name to use when creating the function directory is "uac2".
 725 The uac2 function provides these attributes in its function directory:
 726
 727         =============== ====================================================
 728         c_chmask        capture channel mask
 729         c_srate         capture sampling rate
 730         c_ssize         capture sample size (bytes)
 731         p_chmask        playback channel mask
 732         p_srate         playback sampling rate
 733         p_ssize         playback sample size (bytes)
 734         req_number      the number of pre-allocated request for both capture
 735                         and playback
 736         =============== ====================================================
 737
 738 The attributes have sane default values.
 739
 740 Testing the UAC2 function
 741 -------------------------
 742
 743 device: run the gadget
 744 host: aplay -l # should list our USB Audio Gadget
 745
 746 This function does not require real hardware support, it just
 747 sends a stream of audio data to/from the host. In order to
 748 actually hear something at the device side, a command similar
 749 to this must be used at the device side::
 750
 751         $ arecord -f dat -t wav -D hw:2,0 | aplay -D hw:0,0 &
 752
 753 e.g.::
 754
 755         $ arecord -f dat -t wav -D hw:CARD=UAC2Gadget,DEV=0 | \
 756           aplay -D default:CARD=OdroidU3
 757
 758 18. UVC function
 759 ================
 760
 761 The function is provided by usb_f_uvc.ko module.
 762
 763 Function-specific configfs interface
 764 ------------------------------------
 765
 766 The function name to use when creating the function directory is "uvc".
 767 The uvc function provides these attributes in its function directory:
 768
 769         =================== ================================================
 770         streaming_interval  interval for polling endpoint for data transfers
 771         streaming_maxburst  bMaxBurst for super speed companion descriptor
 772         streaming_maxpacket maximum packet size this endpoint is capable of
 773                             sending or receiving when this configuration is
 774                             selected
 775         =================== ================================================
 776
 777 There are also "control" and "streaming" subdirectories, each of which contain
 778 a number of their subdirectories. There are some sane defaults provided, but
 779 the user must provide the following:
 780
 781         ================== ====================================================
 782         control header     create in control/header, link from control/class/fs
 783                            and/or control/class/ss
 784         streaming header   create in streaming/header, link from
 785                            streaming/class/fs and/or streaming/class/hs and/or
 786                            streaming/class/ss
 787         format description create in streaming/mjpeg and/or
 788                            streaming/uncompressed
 789         frame description  create in streaming/mjpeg/<format> and/or in
 790                            streaming/uncompressed/<format>
 791         ================== ====================================================
 792
 793 Each frame description contains frame interval specification, and each
 794 such specification consists of a number of lines with an inverval value
 795 in each line. The rules stated above are best illustrated with an example::
 796
 797   # mkdir functions/uvc.usb0/control/header/h
 798   # cd functions/uvc.usb0/control/
 799   # ln -s header/h class/fs
 800   # ln -s header/h class/ss
 801   # mkdir -p functions/uvc.usb0/streaming/uncompressed/u/360p
 802   # cat <<EOF > functions/uvc.usb0/streaming/uncompressed/u/360p/dwFrameInterval
 803   666666
 804   1000000
 805   5000000
 806   EOF
 807   # cd $GADGET_CONFIGFS_ROOT
 808   # mkdir functions/uvc.usb0/streaming/header/h
 809   # cd functions/uvc.usb0/streaming/header/h
 810   # ln -s ../../uncompressed/u
 811   # cd ../../class/fs
 812   # ln -s ../../header/h
 813   # cd ../../class/hs
 814   # ln -s ../../header/h
 815   # cd ../../class/ss
 816   # ln -s ../../header/h
 817
 818
 819 Testing the UVC function
 820 ------------------------
 821
 822 device: run the gadget, modprobe vivid::
 823
 824   # uvc-gadget -u /dev/video<uvc video node #> -v /dev/video<vivid video node #>
 825
 826 where uvc-gadget is this program:
 827         http://git.ideasonboard.org/uvc-gadget.git
 828
 829 with these patches:
 830
 831         http://www.spinics.net/lists/linux-usb/msg99220.html
 832
 833 host::
 834
 835         luvcview -f yuv
 836
 837 19. PRINTER function
 838 ====================
 839
 840 The function is provided by usb_f_printer.ko module.
 841
 842 Function-specific configfs interface
 843 ------------------------------------
 844
 845 The function name to use when creating the function directory is "printer".
 846 The printer function provides these attributes in its function directory:
 847
 848         ==========      ===========================================
 849         pnp_string      Data to be passed to the host in pnp string
 850         q_len           Number of requests per endpoint
 851         ==========      ===========================================
 852
 853 Testing the PRINTER function
 854 ----------------------------
 855
 856 The most basic testing:
 857
 858 device: run the gadget::
 859
 860         # ls -l /devices/virtual/usb_printer_gadget/
 861
 862 should show g_printer<number>.
 863
 864 If udev is active, then /dev/g_printer<number> should appear automatically.
 865
 866 host:
 867
 868 If udev is active, then e.g. /dev/usb/lp0 should appear.
 869
 870 host->device transmission:
 871
 872 device::
 873
 874         # cat /dev/g_printer<number>
 875
 876 host::
 877
 878         # cat > /dev/usb/lp0
 879
 880 device->host transmission::
 881
 882         # cat > /dev/g_printer<number>
 883
 884 host::
 885
 886         # cat /dev/usb/lp0
 887
 888 More advanced testing can be done with the prn_example
 889 described in Documentation/usb/gadget_printer.rst.
 890
 891
 892 20. UAC1 function (virtual ALSA card, using u_audio API)
 893 ========================================================
 894
 895 The function is provided by usb_f_uac1.ko module.
 896 It will create a virtual ALSA card and the audio streams are simply
 897 sinked to and sourced from it.
 898
 899 Function-specific configfs interface
 900 ------------------------------------
 901
 902 The function name to use when creating the function directory is "uac1".
 903 The uac1 function provides these attributes in its function directory:
 904
 905         ========== ====================================================
 906         c_chmask   capture channel mask
 907         c_srate    capture sampling rate
 908         c_ssize    capture sample size (bytes)
 909         p_chmask   playback channel mask
 910         p_srate    playback sampling rate
 911         p_ssize    playback sample size (bytes)
 912         req_number the number of pre-allocated request for both capture
 913                    and playback
 914         ========== ====================================================
 915
 916 The attributes have sane default values.
 917
 918 Testing the UAC1 function
 919 -------------------------
 920
 921 device: run the gadget
 922 host: aplay -l # should list our USB Audio Gadget
 923
 924 This function does not require real hardware support, it just
 925 sends a stream of audio data to/from the host. In order to
 926 actually hear something at the device side, a command similar
 927 to this must be used at the device side::
 928
 929         $ arecord -f dat -t wav -D hw:2,0 | aplay -D hw:0,0 &
 930
 931 e.g.::
 932
 933         $ arecord -f dat -t wav -D hw:CARD=UAC1Gadget,DEV=0 | \
 934           aplay -D default:CARD=OdroidU3